Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394...

[~andy/linux] / Documentation / kbuild / kconfig-language.txt

diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
index b507d61fd41cd6a20157dca27f38a28b98f4fa1d..44e2649fbb295db936245c4c0de09109738bfc5e 100644 (file)
--- a/Documentation/kbuild/kconfig-language.txt
+++ b/Documentation/kbuild/kconfig-language.txt
@@ -113,6 +113,13 @@ applicable everywhere (see syntax).
        That will limit the usefulness but on the other hand avoid
        the illegal configurations all over.
 
        That will limit the usefulness but on the other hand avoid
        the illegal configurations all over.
 

+- limiting menu display: "visible if" <expr>
+  This attribute is only applicable to menu blocks, if the condition is
+  false, the menu block is not displayed to the user (the symbols
+  contained there can still be selected by other symbols, though). It is
+  similar to a conditional "prompt" attribude for individual menu
+  entries. Default value of "visible" is true.
+

 - numerical ranges: "range" <symbol> <symbol> ["if" <expr>]
   This allows to limit the range of possible input values for int
   and hex symbols. The user can only input a value which is larger than
 - numerical ranges: "range" <symbol> <symbol> ["if" <expr>]
   This allows to limit the range of possible input values for int
   and hex symbols. The user can only input a value which is larger than


@@ -303,7 +310,8 @@ menu:
        "endmenu"
 
 This defines a menu block, see "Menu structure" above for more
        "endmenu"
 
 This defines a menu block, see "Menu structure" above for more

-information. The only possible options are dependencies.
+information. The only possible options are dependencies and "visible"
+attributes.

 
 if:
 
 
 if:
 


@@ -381,3 +389,25 @@ config FOO
 
 limits FOO to module (=m) or disabled (=n).
 
 
 limits FOO to module (=m) or disabled (=n).
 

+Kconfig symbol existence
+~~~~~~~~~~~~~~~~~~~~~~~~
+The following two methods produce the same kconfig symbol dependencies
+but differ greatly in kconfig symbol existence (production) in the
+generated config file.
+
+case 1:
+
+config FOO
+       tristate "about foo"
+       depends on BAR
+
+vs. case 2:
+
+if BAR
+config FOO
+       tristate "about foo"
+endif
+
+In case 1, the symbol FOO will always exist in the config file (given
+no other dependencies).  In case 2, the symbol FOO will only exist in
+the config file if BAR is enabled.